Opened 6 years ago

Last modified 3 years ago

#15249 new defect

In lazy power series rings, 0 + a and 0 - a return 0

Reported by: darij Owned by:
Priority: major Milestone: sage-6.4
Component: algebra Keywords: LazyPowerSeries, species
Cc: mhansen, mantepse Merged in:
Authors: Reviewers:
Report Upstream: N/A Work issues:
Branch: Commit:
Dependencies: Stopgaps: incorrectAnswerMarker

Description

sage: L = LazyPowerSeriesRing(QQ)
sage: x = L.gen()
sage: L.zero().coefficients(4)
[0, 0, 0, 0]
sage: x.coefficients(4)
[0, 1, 0, 0]

Correct so far...

sage: (L.zero() + x).coefficients(4)
[0, 0, 0, 0]
sage: (L.zero() - x).coefficients(4)
[0, 0, 0, 0]

But x - L.zero() and x + L.zero() return correct results.

See also #15248 for another lazy power series bug.

Change History (10)

comment:1 Changed 5 years ago by mantepse

One problem is in series_order.py. There, a very simple lattice (in fact, a total order) should be implemented: NonNegativeIntegers? together with the two special values unknown and infinity. unknown is the minimal element, infinity the maximal element.

Comparing unknown with another element works, comparing infinity with another element works, but comparing an integer with unknown does not work, because the comparison invoked is from Integer.

How should I create such a lattice really?

comment:2 Changed 5 years ago by mantepse

  • Cc mantepse added

comment:3 follow-up: Changed 5 years ago by mhansen

I've done some work on species recently which fixes this as a side effect. This is related to #10084. I'll post the branch asap.

comment:4 Changed 5 years ago by mantepse

  • Keywords LazyPowerSeries added; lazy-power-series removed

comment:5 in reply to: ↑ 3 Changed 5 years ago by mantepse

Replying to mhansen:

I've done some work on species recently which fixes this as a side effect. This is related to #10084. I'll post the branch asap.

Great! I'm all set to dig into the species code too. For a start, I looked through the tickets that are related to the lazy power series code and changed the keyword to LazyPowerSeries?...

Did you see #10931? I guess the patch won't apply anymore, but the philosophy should :-)

Best, Martin

comment:6 Changed 5 years ago by mhansen

A fix is in #15673

comment:7 Changed 5 years ago by vbraun_spam

  • Milestone changed from sage-6.1 to sage-6.2

comment:8 Changed 5 years ago by vbraun_spam

  • Milestone changed from sage-6.2 to sage-6.3

comment:9 Changed 5 years ago by vbraun_spam

  • Milestone changed from sage-6.3 to sage-6.4

comment:10 Changed 3 years ago by jakobkroeker

  • Stopgaps set to incorrectAnswerMarker
Note: See TracTickets for help on using tickets.